#!/usr/bin/env python3
# coding: utf-8

import sys
from PyQt5.QtWidgets import QWidget,QMessageBox, QApplication

class CloseDemo2(QWidget):

    def __init__(self):
        super().__init__()

        self.initUI()

    def initUI(self):
        self.setGeometry(300,300,300,300)
        self.setWindowTitle('closeDemo2')
        self.show()

    def closeEvent(self, event):
        reply = QMessageBox.question(self, "Message", "Are you sure to quit?", QMessageBox.Yes |
                                     QMessageBox.No, QMessageBox.No)

        if reply == QMessageBox.Yes:
            event.accept()
        else:
            event.ignore()


if __name__ == '__main__':

    app = QApplication(sys.argv)
    ex = CloseDemo2()
    sys.exit(app.exec_())